MFA for 5.6 lenses?

Dec 23, 2015
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#1
Sorry if this has been asked before, but do I need to MFA my 5.6 lenses? I have Canon EF 400mm 5.6, EF-S18-55 mm 3.5/5.6 and EF-S 17-85 mm 4/5.6. These two zooms are only used at f5.6. I also have the EF 70-200 f4 IS. Cameras are a 7D2 and a 6D. I ask because a friend said only lenses less that f4 need to be microfocussed because the other lenses have more depth of field to cover focusing errors.
 

Mt Spokane Photography

I post too Much on Here!!
Mar 25, 2011
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#2
It depends on how far off the lens is. Generally, you should not need to, but I've had lenses be way off. The distance to the subject is also a factor, with close distances being more prone to AF errors. I'd just check the lens, its so easy. Put it on a tripod, take 10 shots adjusting the focus to be at the opposite distance to the target so it has to focus again each time. At least 9 of 10 should be in sharp focus.
Another way is to compare live autofocus with phase detect shots to see if the live focus is significantly sharper. Live AF is generally as good as autofocus gets.

The most appealing feature of a mirrorless camera is that autofocus is always accurate as long as you pick a proper target. The issues of low contrast, or other factors like not being on the right spot are user errors, not system errors. I still make those mistakes even with my R. Lenses that tend to have issues with accurate autofocus can often be very accurate with mirrorless.(If a lens has a mechanical issue and is binding internally, its always going to be a dog)
 
Likes: AlanF
Dec 9, 2013
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#3
The focal length matters a great deal. Shooting a subject 20 feet away, a 17mm F5.6 lens will have acceptable focus from about 5 feet in front of the lens to infinity. A 400mm F5.6 lens will have an acceptable focus depth of field of only a few inches.
 
Likes: AlanF
Aug 16, 2012
4,587
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#4
You have to check with the 400mm lens because of the narrow depth of field. Do as Mt S suggests comparing live view with one shot AF, and proceed from there. Your friend 's advice is pretty poor.
 
Aug 1, 2017
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#5
AFMA is a solution in search of a problem for most lenses. Unless you know exactly what you are trying to "fix" you are far more like to make AF worse. I think Canon includes this "feature" because they know compulsive camera tinkerers love it. The idea that every lens needs to be "calibrated" with AFMA is not supported by my experience.
 

Mt Spokane Photography

I post too Much on Here!!
Mar 25, 2011
15,047
413
#6
AFMA is a solution in search of a problem for most lenses. Unless you know exactly what you are trying to "fix" you are far more like to make AF worse. I think Canon includes this "feature" because they know compulsive camera tinkerers love it. The idea that every lens needs to be "calibrated" with AFMA is not supported by my experience.
I find that about half of my lenses benefit by AFMA, I've checked dozens over the years. I was among the first to pre-order Focal. It will show you when your lens is not focusing accurately.

Canon included it because it saved them money. Rather than have people shipping their lens back for adjustment, they can do it themselves. It was first offered on 1 series cameras.

The recent "L" lenses like the 24-70mm L II and 70-200mm L II as well as my 100-400mm L II seem to be more accurate, but the 24-70 needed about 5 points. Lenses like my 35mm L needed 17 points, so I sent it to Canon and it came back perfect. Some like my 100mm L need 10 pts which is borderline, so I use it with the AFMA adjustment. I bought a Sigma 15-30mm f/1.8, it was way off, and unfortunately, the camera I intended to use it with did not have AFMA, so it was trial and error to get it reasonably close using their dock.

Third party lenses benefit the most, because they don't emulate Canon's protocol perfectly and AF accuracy can vary based on the body. They can be adjusted with a dock in many cases, but only if you know how to set them, and AFMA is needed to do that unless you want to do hundreds of trial and error tests.